In ported type style gate valve bodies the seat ring is pressed into an annular groove in the valve body. In non-ported style gate valve bodies a seat pocket is formed in the body and opens to the flow passageway so the seat ring when inserted has its interior portion opening to the flow passageway through the valve body. In the prior art seat rings for non-ported valve bodies have been typically pressed in place and retained by an interference fit between the valve body and the exterior of the seat ring or they are threadedly mounted in the body. While pressing in the seat ring is desirable and acceptable in small valves, it is unacceptable in the larger pipeline size valves which have an internal diameter from between one foot to five feet and larger.
Retaining the seat rings in large gate valve bodies is a perplexing problem in the art particularly during assembly and servicing of the valves because the seats must be kept in place while the gate is installed. During use of such a valve, the seats must be kept in place as the gate moves between open and closed position and during high velocity flow.
Retaining clips are known in the arts to retain seat rings in place, however they consist of wire clips which are inserted into the bonnet and secure edge portions of the seat ring where they extend beyond the valve body toward the gate. This type of structure is not usable in the instance where the seat ring does not extend past the body toward the gate or extends only a slight amount past the body. Another seat ring retainer structure involves the placing of a lug at a bottom portion of the valve body at a point where it will support the gate side of the seat ring at a point where it will not interfere with the motion of the gate, and mounting a removable lug in an upper portion of the valve body in a position extending over an upper portion of the seat ring. While this particular structure is adequate, the removably mounted lug is difficult, if not impossible, to remove and replace after a valve has been in service for some time. Other seat retaining structures are known which incorporate a plurality of lugs about the interior of the valve body to retain the seat ring in combination with a fourth lug or supporting structure on the valve bonnet. No specific device is known in the art which secures the seat ring to the valve body by using a fastener structure positioned on the interior of the flow passageway of the valve body.